BOSTON – House Speaker Robert DeLeo has opened an investigation into allegations that freshman Democratic Rep. Mark Cusack engaged in inappropriate behavior with another lawmaker’s aide in the House chamber in the hours after a House budget session in April.

Multiple sources within the Legislature and outside of the State House said that Cusack and the young woman were discovered by a court officer in the well of the rostrum in the pre-dawn hours following the conclusion of the House budget debate.

“The House will conduct an internal review of this matter,” DeLeo spokesman Seth Gitell said in a statement in response to an inquiry from the News Service.

Cusack, a 26-year-old freshman from Braintree who previously served as an assistant to Braintree Mayor Joe Sullivan, was first elected to the House in November 2010. He represents the 5th Norfolk District, a seat previously held by Joseph Driscoll.

Mark Cusack

The State House buzzed Friday with lawmakers and staffers claiming the alleged incident was reminiscent of the infamous, late-night boozy budget session in 2000 when debate carried into the early morning hours and one dozing lawmaker reportedly had his leg shaved.

A source indicated that both Cusack and the woman were clothed, and multiple sources indicated that Cusack initially gave the court officer the name of another freshman Democrat in House.

Cusack did not respond to emailed requests for comment on Friday, and someone that answered the phone at his home said he was not available. The freshman Republican House lawmaker whose aide was reportedly involved also could not be reached for comment.

Cusack graduated from Braintree High School in 2000, and the University of Massachusetts Amherst in 2007. He was an intern for U.S. Rep. Stephen Lynch, and became the assistant to the Mayor Sullivan in 2007.

Asked about the reports of Cusack’s behavior, one Democratic House member said it paints all lawmakers in a bad light.

“This just makes everybody look bad. It’s Animal House all over again and makes us look like we’re a joke,” said the legislator, who asked not to be named.